Mozilla sent a cease-and-desist letter on Tuesday to a European company that created a piece of spyware masquerading itself as the Firefox browser.

The move comes after computer security researchers said on Tuesday that they discovered that a well-known spyware program called FinSpy was spoofing Firefox. Mozilla was alerted by the researchers, who are with Citizen Lab, a research project that is part of the University of Toronto's Munk School of Global Affairs.

FinSpy is one component in a set of remote interception and intrusion tools called FinFisher, which is made by a subsidiary of U.K-based Gamma Group called Gamma International.

Citizen Lab has done extensive research into FinSpy and found it is being used in a number of countries with poor human rights records and has been used to target activists. It is considered by some to be malicious software.

On Tuesday, Citizen Lab released a summary of its latest findings. FinSpy makes use of Mozilla's trademark and code, wrote researchers Morgan Marquis-Boire, Bill Marczak, Claudio Guarnieri and John Scott-Railton.

"The latest Malay-language sample masquerades as Mozilla Firefox in both file properties and in manifest," they wrote. "This behavior is similar to samples discussed in some of our previous reports, including a demo copy of the product, and samples targeting Bahraini activists."

Hackers often dress up malicious files to make them appear to be benign, piggybacking on the inherent trust users put into known programs. Appearing to be Firefox makes it more likely potential victims will be duped into installing FinSpy.

Citizen Lab plans to release its latest report, "For Their Eyes Only: The Commercialization of Digital Spying," early Wednesday morning EST, which includes new findings on the proliferation of FinFisher.

The group said it found FinFisher command-and-control servers in 11 new countries: Hungary, Turkey, Romania, Panama, Lithuania, Macedonia, South Africa, Pakistan, Nigeria, Bulgaria, and Austria. The report also summarizes one year of research Citizen Lab has done into the commercial market for offensive intrusion tools developed by Western companies.